According to Wikipedia each ASCII printiable character has 6.570 bits of entropy, so if your password is truly randomly generated, thirteen characters is only equal to 85.41 bits of entropy. That is not a horrible password, for a long time the minimum entropy of a secure password was considered to be 80 bits, but today estimates are closer to 128 bits. 80 bit passwords are no longer considered to be secure, 85 bit passwords are significantly better but you really should aim for at least 128 bits, which is about 20 random ASCII characters or 128 characters of English text.